1. Field of the Invention
The present invention relates to a scanning type display optical system and a scanning type image display apparatus, which display images by scanning light.
2. Description of Related Art
Generally, scanning type image display apparatuses are characterized by having high resolution, and various structures have been proposed.
For example, a laser display is reported in “Kogaku Gijutsu Contact (meaning Optical Technology Contact) Vol. 21, No. 6-7″ (1983). This obtains high-quality TV pictures by modulating laser beams with an optical modulator and two-dimensionally scanning the modulated beams with a polygon mirror and a galvano-mirror at a high speed. Furthermore, a similar art is proposed in Japanese Patent Application Laid-Open No. 2000-180759.
These image display apparatuses realize high-speed horizontal scanning by using a polyhedral mirror (polygon mirror). Concretely, in order to make the horizontal scanning rate high, a polygon mirror having eight or more reflective surfaces is used.
On the other hand, recently, a device called Micro Electro Mechanical System (hereinafter, referred to as MEMS) using semiconductor production technology has been developed.
Machinery produced by using MEMS technology is very small in size and light in weight, and has very quick response, and application of this system to various fields is being considered. Particularly, development in the field called MOEMS (Micro Optical Electro Mechanical System) obtained by applying MEMS to optics is active, and scanning devices using MEMS technology have been developed.
A technique relating to an image display apparatus using a scanning device using such MEMS technology has been proposed in Japanese Patent Application Laid-Open No. 2001-281583. In this Laid-Open 2001-281583, a scanning optical system has been proposed which two-dimensionally scans a projection surface by two-dimensionally deflecting light emitted from a light source with a scanning device, wherein a small-sized scanning optical system is realized by the scanning device and an optical system including a rotationally asymmetric surface prepared by MEMS technology.
In the abovementioned laser display reported in “Kogaku Gijutsu Contact (meaning Optical Technology Contact) Vol. 21, No. 6-7 (1983)” or in the scanning optical system proposed in Japanese Patent Application Laid-Open No. 2000-180759, a polygon mirror having eight reflective surfaces is used as the scanning device. This easily results in an increase in size of the scanning device since the number of reflective surfaces is large in one optical device although high-speed scanning is possible.
Furthermore, in Japanese Patent Application Laid-Open No. 2001-281583, a scanning device shown in FIG. 3 of this publications is used. Namely, a scanning device which scans light by oscillating the reflective surface biaxially is used. However, since biaxial scanning is carried out by one reflective surface, the structure of the scanning device becomes complicated or the device increases in size.